Two Species Of Stickleback Fish Disappear From Canada Lake After Scientists Introduced Crayfish

Scientists are surprised at what happened in Enos Lake on Vancouver Island of Canada after they introduced crayfish to the lake. It was total extinction of two endangered species of threespine stickleback fish, and an evolution of crossbreeds of the two extinct species.

This incident occurred within three years, between 1994 and 1997, after the introduction of the crayfish according to a study published in the journal Current Biology.

This event makes researchers to understand that humans can speed up evolution by introducing a new species into an ecosystem, creating subsequent changes in the ecosystem – a process that has come to be known as “reverse speciation”.

"When two similar species are in one environment, they often perform different ecological roles," said Seth Rudman, a PhD student in zoology at UBC. "When they go extinct, it has strong consequences for the ecosystem."

One of the extinct threespine stickleback fish lived in the middle of the lake and ate zooplankton and the other species lived closer to the shore and fed on larva and other insects. Within three years of introducing crayfish to the lake, the two stickleback fish disappeared only to be replaced with an interbred, hybrid species.

Unfortunately, the new hybrid species does not function like its predecessors to maintain balance in the ecosystem. This species consumes large insects close to the shore, causing tiny insects emerging from the lake to increase in a demonstration of the fact that changes to a lake would cause changes on the land surrounding it.

"Much of Canada's biodiversity, particularly fish in lakes and rivers, are considered to be 'young' species that formed in the last 12,000 years or so," said Rudman. "This type of evolution, known as reverse speciation, happens remarkably quickly and can cause alterations to the ecology of the ecosystem. It means we need to consider evolution in our conservation efforts."

Rudman and co-author Dolph Schluter, a professor in UBE’s department of zoology noted that this case of reverse speciation shows up in ecosystems altered by human activity.

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